JP2011251394A - Electrode wire for electric discharge machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode wire for electric discharge machining capable of not only improving the cutting accuracy of a workpiece but also improving a machine speed by restraining reduction in tensile strength even if discharge energy is increased.SOLUTION: The electrode wire for the electric discharge machining is characterized in that the outer periphery of a conductor is covered with nickel (Ni) with a stainless steel wire as a conductor, and then, successively covered with copper (Cu) and zinc (Zn), and desirably, a thickness of the nickel (Ni) is 0.01-2.0 μm, and tensile strength at the ordinary temperature of the electrode wire is 1900-3200N/mm, and the tensile strength of the electrode wire at 400°C is 70% or higher of the tensile strength at the ordinary temperature.

Description

  The present invention relates to an electrode wire for electric discharge machining.

  In precision wire electric discharge machining used for molds of semiconductor lead frames, etc., the diameter of electrode wires has been reduced. In particular, the high-strength high-strength high-carbon steel wire is essential for the electrode wire for small-diameter electric discharge machining with a wire diameter of 0.1 mm or less, and an alloy of Cu and Zn that improves electric discharge workability on the outer periphery of the core wire. A covering layer or a two-layer structure of Cu as the first layer and Zn as the second layer has been commercialized and distributed.

  However, since these electrode wires are exposed to high temperatures during electric discharge machining, materials having low heat resistance cannot be processed with high tension during electric discharge machining. For this reason, there has been a problem that the vibration of the electrode wire is increased due to the explosion caused by the rapid increase in temperature, and the cutting accuracy is deteriorated.

  Various proposals have been made regarding the electrode wire for electric discharge machining. For example, Japanese Patent Laid-Open No. 03-111126 (the following Patent Document 1) discloses a metal wire such as a hard steel wire, a stainless steel wire, or a brass wire. By forming a copper coating layer on the surface of this, and further forming a zinc coating layer thereon, a coating layer having a two-layer structure having a total coating layer thickness of 0.2 to 20 μm is formed. By dispersing graphite particles having an average particle diameter of 10 μm or less over one or both of the coating layers, copper is melted by heat from electric discharge machining, and is stable without being fused to the workpiece. An electrode wire for electric discharge machining is described in which electric discharge is obtained and the machining speed can be improved.

  However, the method of Patent Document 1 has a problem that it is necessary to disperse graphite particles in the coating, and the manufacturing process is complicated and the manufacturing cost is high.

Japanese Patent Application Laid-Open No. 09-103922 (Patent Document 2 below) describes a stainless steel having a tensile strength of 200 to 300 Kgf / mm ² and a wire diameter of 0.05 to 0.20 mm, and has an electrical conductivity of 1. By being ~ 3%, the machining accuracy and surface roughness of the workpiece can be dramatically improved, no surface polishing step after electric discharge machining is required, and the manufacturing cost of the electrode wire and the maintenance of the electric discharge machine are maintained. An electrode wire for wire electric discharge machining that can reduce the management cost is described.

  However, since Patent Document 2 uses a stainless steel wire that is not coated, there is a problem in that electric discharge machining performance is not sufficient.

Japanese Patent Laid-Open No. 03-111126 Japanese Patent Laid-Open No. 09-103922

  The present invention solves the problems of the prior art as described above, can suppress the decrease in tensile strength even when the discharge energy is increased, can improve the cutting accuracy of the workpiece, and improve the processing speed. It is an object of the present invention to provide an electrode wire for electric discharge machining that can be made to occur.

The present invention has been made as a result of intensive studies in order to solve the above-described problems, and the gist of the present invention is the following contents as described in the claims.
(1) An electrode wire in which a stainless steel wire is used as a core wire, the outer periphery of the core wire is coated with nickel (Ni), and then copper (Cu) and zinc (Zn) are sequentially coated with a tensile strength of 1900 N / mm An electrode wire for electric discharge machining characterized by being ² or more.
(2) The electrode wire for electric discharge machining according to (1), wherein the nickel (Ni) has a thickness of 0.01 to 2.0 μm.
(3) The tensile strength of the electrode wire at normal temperature is 1900-3200 N / mm ² , and the tensile strength at 400 ° C. of the electrode wire is 70% or more of the tensile strength at normal temperature. The electrode wire for electric discharge machining according to (1) or (2).
(4) The electrode wire for electric discharge machining according to any one of (1) to (3), wherein an outer diameter of a cross section of the electrode wire after drawing is φ0.03 mm to 0.1 mm .
(5) The electrode wire for electric discharge machining according to any one of (1) to (4), wherein a heat treatment for alloying the copper (Cu) and zinc (Zn) is performed.
(6) The electrode wire for electric discharge machining as described in any one of (1) to (5), wherein straight processing is performed by hot tensile processing.

  ADVANTAGE OF THE INVENTION According to this invention, even if it increases discharge energy, the fall of tensile strength can be suppressed, the cutting precision of a workpiece can be improved, and the electrode wire for electrical discharge machining which can improve a processing speed is provided. It has a significant industrially useful effect.

The best mode for carrying out the present invention will be described below. FIG. 1 is a cross-sectional view illustrating an electrode wire for electric discharge machining according to the present invention. As shown in FIG. 1 (a), the electrode wire for electric discharge machining according to the present invention has a stainless steel wire as a core wire 1, the outer periphery of the core wire 1 is coated with nickel (Ni) 2, and then copper (Cu) 3 and It is an electrode wire coated with zinc (Zn) 4 in sequence, and has a tensile strength of 1900 N / mm ² or more.

  In the electric discharge machining, a stable machining speed and good cutting accuracy can be obtained by applying a high tension to the electrode wire. However, when the discharge energy is increased in order to increase the processing speed, that is, as the voltage and current are increased, the electrode wire is heated. For this reason, even if a high-strength electrode wire is used, if the heat resistance is poor, it cannot be processed with high tension, so that a stable processing speed and good cutting accuracy cannot be obtained.

  In the present invention, by making the core wire a stainless steel wire having excellent heat resistance, high tension can be obtained even when the discharge energy is increased, and the processing speed can be improved. In the present invention, the type of stainless steel is not limited, but stainless steel such as SUS304 and high nitrogen stainless steel that can be increased in strength is preferable from the viewpoint of versatility.

  Moreover, in the conventional electrode wire, since the electrode wire temperature by electric discharge machining rose, it was not possible to reduce the feed rate of the electrode wire.

  Since the electrode wire for electric discharge machining of the present invention is excellent in heat resistance even when the electrode wire temperature rises, the electrode wire feed rate can be lowered to reduce the consumption of the electrode wire.

  Also, the conventional idea of small-diameter EDM electrode wires for precision machining is to apply a high-strength core wire to maintain high strength, and an alloy of Cu and Zn to improve EDM in the outer layer A coating layer such as a coating layer or a two-layer structure of Cu as the first layer and Zn as the second layer was provided. That is, it is made by combining two functions of increasing the strength with the core wire and improving the electrical discharge processability with the outer layer coating.

  With these two functions alone, even if the strength is increased, it is impossible to process with a high tension at a high temperature during electric discharge machining, and thus a stable machining speed and good cutting accuracy cannot be obtained.

  In order to solve the above problems, in the present invention, the core wire has not only high strength but also two functions of high strength and high heat resistance, and then higher thermal diffusibility than the core material and linear expansion. Strain is suppressed by covering nickel (Ni), which is a low-rate material, diffusing heat generated by electric discharge, and reducing expansion. The outermost layer was coated with copper (Cu) and zinc (Zn), which are materials for improving electric discharge machinability. That is, the electrode wire for electric discharge machining according to the present invention is an electrode wire for electric discharge machining having a strength maintaining function, a heat resistance function, a distortion suppressing function, and an electric discharge machining improving function.

  As a result, improvement in the cutting accuracy of the workpiece, which is the subject, and reduction in tension are suppressed even when the discharge energy is increased. That is, improvement of electrical discharge machining. Furthermore, even if the feeding speed of the electrode wire is slowed, an electric discharge machining electrode wire that can be cut in the same amount as in the conventional case, that is, good in economic efficiency can be provided.

Moreover, in order to suppress the heat conduction to the core wire of the heat which generate | occur | produced by discharge, it is preferable that the thickness of the said nickel (Ni) shall be 0.01-2.0 micrometers. The electrode wire has a tensile strength at normal temperature of 1900 to 3200 N / mm ² , and the tensile strength at 400 ° C. of the electrode wire is preferably 70% or more of the tensile strength at normal temperature.

The outer diameter of the electrode wire after drawing is preferably 0.03 mm to 0.1 mm in accordance with the model of the electric discharge machine to be applied.
The copper (Cu) and zinc (Zn) coatings may be independent layers, but the adhesion can be improved by heat treatment and alloying as shown in FIG.

  In addition, by performing straight processing on the electrode wire by hot tensile processing, not only can vibrations during electric discharge processing be further reduced, but also automatic connection can be satisfactorily performed.

  The results of carrying out the present invention under the following conditions are shown in Table 1. The basic manufacturing process of the present embodiment is to use a stainless steel wire or a high carbon steel wire as a core material and apply a coating to provide a necessary function, and perform strong processing to finish the product wire diameter. It has been subjected to straight heat treatment. The examples in the table below were evaluated by finishing with a wire diameter of 0.05 mm.

  Inventive Examples 1 to 8 use SUS304 stainless steel wire (stainless steel A) or stainless steel (stainless steel B) added with nitrogen as the core wire, and coat Ni, then Cu, and then Zn, In some cases, they were heat-treated by alloying, and each of them was subjected to strong processing at different degrees of processing to produce ones having different tensile strengths. In addition, the thickness of Ni at the time of evaluation was set to 0.01 to 0.2 μm, and the thickness of the alloyed Cu and Zn was set to 5 μm. Inventive Examples 1 to 10 have a tensile strength at 400 ° C. of 70% or more compared to the case where the tensile strength at room temperature is 100, and the processing speed is improved by 10% or more compared to Comparative Example 4 which is a conventional material. Confirmed to do.

  Comparative Examples 1 to 4 and Invention Examples 1 to 4 were subjected to diffusion treatment, and Comparative Examples 5 to 8 and Invention Examples 5 to 8 were not subjected to diffusion treatment. In Comparative Example 1, since the Ni coating was not performed, the processing speed was low. Inventive Example 1 was Ni-coated, so the processing speed was high. Invention Example 2 had a Ni coating thickness of 0.15 μm, and the processing speed was the highest among those subjected to diffusion treatment using stainless steel A.

  Invention Example 3 had a Ni coating thickness of 2 μm and a small cross-sectional area of the core wire, so the tensile strength was low, but the processing speed was higher than that of Comparative Example 8. In Comparative Example 2, the Ni coating thickness was 3 μm, the cross-sectional area of the core wire was too small, the tensile strength was low and outside the scope of the invention, and therefore the processing speed was lower than that of Comparative Example 8. In Comparative Example 3, the thickness of the Ni coating was set to 0.15 μm as in Invention Example 2 in which the tensile strength of the core wire was lowered and the processing speed was high, but the processing speed was lower than that in Comparative Example 8. Inventive example 4 used stainless steel B, which has a higher tensile strength than stainless steel A, so that the processing speed was higher than that of stainless steel A.

  Since the core wire was carbon steel, the comparative example 4 had low tensile strength in 400 degreeC. In Comparative Example 5, since Ni coating was not performed, the processing speed was low. Invention Example 5 had a high processing speed by performing Ni coating. Invention Example 6 had a Ni coating thickness of 0.15 μm, and the processing speed was the highest among those in which stainless steel A was not used for diffusion treatment. Invention Example 7 had a Ni coating thickness of 2 μm and a small cross-sectional area of the core wire, so the tensile strength was low, but the processing speed was higher than that of Comparative Example 8.

  In Comparative Example 6, the thickness of the Ni coating was 3 μm, the cross-sectional area of the core wire was too small, the tensile strength was low and outside the scope of the invention, and therefore the processing speed was smaller than that of Comparative Example 8. In Comparative Example 7, the thickness of the Ni coating was set to 0.15 μm as in Invention Example 6 in which the tensile strength of the core wire was reduced and the processing speed was high, but the processing speed was lower than that in Comparative Example 8. Inventive Example 8 used stainless steel B, which has a higher tensile strength than stainless steel A, so that the processing speed was higher than that of stainless steel A. Since Comparative Example 8 was a carbon steel, the tensile strength at 400 ° C. was low. The effects of the present invention were confirmed by the above examples.

It is sectional drawing which illustrates the electrode wire for electrical discharge machining of this invention.

1 Core wire 2 Ni coating 3 Cu coating 4 ZN coating 5 Cu and Zn alloying coating

Claims (6)

An electrode wire having a stainless steel wire as a core wire, the outer periphery of the core wire being coated with nickel (Ni), and then sequentially coated with copper (Cu) and zinc (Zn), and having a tensile strength of 1900 N / mm ² or more An electrode wire for electric discharge machining, characterized in that there is.   The electrode wire for electric discharge machining according to claim 1, wherein the nickel (Ni) has a thickness of 0.01 to 2.0 μm. The tensile strength of the electrode wire at normal temperature is 1900 to 3200 N / mm ² , and the tensile strength of the electrode wire at 400 ° C. is 70% or more of the tensile strength at normal temperature. The electrode wire for electric discharge machining according to claim 1 or 2.   The electrode wire for electric discharge machining according to any one of claims 1 to 3, wherein an outer diameter of a cross section of the electrode wire after wire drawing is 0.03 mm to 0.1 mm.   The electrode wire for electric discharge machining according to any one of claims 1 to 4, wherein a heat treatment for alloying the copper (Cu) and zinc (Zn) is performed. The electrode wire for electric discharge machining according to any one of claims 1 to 5, wherein straight machining is performed by hot tensile machining.

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